As the use of composite materials increases, the development of advanced nondestructive testing (NDT) techniques for composite materials is in demand. Ultrasonic quantitative NDT techniques for composite materials may provide good information on manufacturing quality, material strength and perhaps useful lifetime. Additionally, the effects of porosity in composite laminates on ultrasonic attenuation can be used in gauging the porosity content in composite material.
Ultrasonic NDT techniques require a porosity reference standard to calibrate the measurements for a composite component provided by the ultrasonic testing equipment. Unfortunately, the process of fabricating porosity reference standards is complicated, time consuming, and very expensive. Typically this process requires large numbers of composite coupons to be fabricated and many testing sites or samples to be taken for porosity measurements. Selection of testing sites is essentially random, which requires iterations of coupon fabrication and porosity measurements to form reference standards representing a range of percent porosities.
Additionally, porosity standards fabricated using artificial materials to simulate porosity may not provide accurate attenuation measurements when compared to natural porosity occurring in a composite component.
Accordingly, those skilled in the art continue with research and development efforts in the field of fabrication of reference porosity standards.